Simulated physiological structures that can provide feedback related to simulated medical procedures performed on such structures are very useful as medical training aids. As a result, the use of simulated physiological structures for training medical students and providing skill training for practicing physicians is widespread. Although cadavers have traditionally been beneficially employed for this purpose, cadavers are not always readily available and are not well suited for all types of training.
Simulated physiological structures should preferably be usable repeatedly and should provide a realistic training experience corresponding to what the trainee would expect if applying a procedure on an actual patient. Students, and even practicing physicians and nurses, often need to be tested to determine their skill level with respect to certain procedures. Since an objective standard is preferable in conducting such tests, a simulated physiological structure should include systems for providing feedback indicating how well the student or physician is performing a simulated task.
The need for such simulators should not be underestimated, because they can provide valuable training that will lead to more effective treatment of patients. For example, medical personnel who administer emergency trauma care can greatly benefit from the training achieved using a simulated physiological structure. Training in administering trauma surgical procedures, which include those procedures that are usually performed on a person who has experienced some form of severe and often life-threatening injury, is particularly beneficial. Such procedures may aid in the diagnosis of a condition, or may provide immediate life-saving care until more complete medical treatment is available. The procedures may include clearing a blocked airway or draining accumulations of fluids from internal organs. While appearing to be simple procedures, if these procedures are performed improperly, the result can worsen the patient's condition, placing the patient at an even greater peril of death. By their nature, trauma procedures are usually performed under emergency conditions in which the person administering the care is under time-related stress. It is therefore useful to provide training methods and apparatus to fully prepare students and physicians in these procedures, so that they can be performed without delay, under stressful conditions.
It should be noted that one reason why the use of a training model (either a cadaver, an animal, or a simulator) is desirable is that while anatomy follows general rules, variations based on sex, age, height, and weight are the norm. A surgical student cannot simply be provided directions such as “make an incision four inches long and two inches deep, starting at the navel.” Normal variations such as the amount of body fat will significantly change the depth of fat tissue that must be incised to reach an internal organ. Surgeons must rely on their knowledge of general anatomy, and visual cues (i.e., the patient has low body fat, the patient has high body fat, the patient is a child, the patient is an adult, the patient is a female, etc.) to determine the correct location on a specific patient for performing a procedure. The use of cadavers, animal models, and anatomically correct simulators enable surgical students to apply their knowledge of anatomy to determine the proper position for executing a procedure.
To provide the desired level of realism, a simulated physiological structure used for training medical personnel should provide tactile sensations during a simulated procedure that faithfully portray the tactile sensations experienced during an actual procedure performed on a patient. Human anatomical models have been proposed using elastomeric compositions for human tissue. However, most elastomeric-based simulators that have previously been created do not include a level of detail that faithfully portrays the finer aspects of human tissue, including the tactile feel of different types of tissue. Commonly owned U.S. Pat. No. 6,780,016 discloses details of a human surgical trainer that provides very realistic tactile simulated tissue.
Even if a simulated physiological structure having simulated tissue faithfully portrays finer details of an actual physiological structure and provides a realistic tactile sensation during a simulated procedure, prior simulators do not include means for producing objective and measurable results that can be used to evaluate how well a simulated procedure is performed. Clearly, it would be desirable to employ a simulated physiological structure that is able to provide a realistic tactile sensation during a simulated procedure, and which is also able to provide an objective indication that can be used to evaluate how well a simulated procedure was executed.
One of the key requirements for such a simulator is that physically flexible electrical circuitry be included within the elastomeric material that represents tissue and other flexible organic elements, without changing the tactile characteristics of the elastomeric material. For example, flexible elastomeric conductive materials can be employed to produce flexible circuits that would be usable in a simulator. Sanders et al. (U.S. Pat. No. 5,609,615) discloses a cardiac simulator including an electrically conductive polymer. Thus, medical devices including electrically conductive polymers are known in the art. Indeed, other patents disclose the use of electrically conductive polymers in medical treatment devices (see for example: U.S. published patent application No. 2001/0000187 (Peckham et al.) describing prosthetics; U.S. Pat. No. 6,532,379 (Stratbucker) describing a defibrillator lead; U.S. Pat. No. 6,095,148 (Shastri et al.) describing a neural stimulator; U.S. Pat. No. 4,898,173 (Daglow et al.) describing an implantable electrical connector; PCT application WO 01/32249 (Geddes et al.) describing a tracheotrode; EPO application No. 0601806A2 (Moaddeb et al.) describing a cardiac stimulating electrode; and EPO application No. 0217689 (Compos) describing an ultrasound transducer). Each of the Toth references (U.S. Pat. Nos. 6,540,390; 6,436,035; and 6,270,491) discloses a surgical light that includes a user-actuatable switch that is constructed using conductive elastomers. Kanamori (U.S. Pat. No. 4,273,682) discloses a pressure sensitive conductive elastomer, but not in the context of a simulated physiological structure. Soukup et al. (U.S. Pat. No. 5,205,286) describes an implantable data port that employs an electrically conductive polymer to enable data to be conveyed from an implanted medical device or sensor to an externally disposed data dump. While the data port includes a conductive elastomer, the circuit does not provide evaluation data regarding a simulated procedure and is not part of a simulated physiological structure used for training purposes.
Commonly owned U.S. Pat. No. 8,556,635, discloses a nerve block trainer that includes conductive elastomers, which simulate the conductivity of human nerves. The function of the nerve block trainer is to train medical personnel to insert a needle properly when administering a nerve block. This training system uses a needle that is connected to a power source, and when the needle is inserted into the tissue and comes into contact with the conductive elastomer, it completes the circuit. The contact of the needle with conductive elastomers is interpreted by an electronic circuit that sends a signal to a personal computer (PC) through a Universal Serial Bus (USB) port. The signal is interpreted by software executing on the PC and is presented on the screen as a visual image of the targeted site that includes highlights on the screen indicating when the needle has come into contact with a specific targeted site.
While the use of conductive elastomers in a medical training simulator is very effective, there are certain training procedures relating to the insertion of a needle or contact between a different type of medical instrument with a simulated vessel that would be more effectively implemented by directly detecting when the needle or medical instrument actually contacts a fluid simulating blood being conveyed within the simulated vessel. For example, if the medical procedure requires that a needle be inserted into the internal jugular vein of the simulator, but not into its carotid artery, it would be desirable to be able to detect contact by the needle with the simulated blood in either of these vessels, and thereby, to determine if the person controlling the needle has inadvertently come into contact with or pierced the carotid artery or has failed to properly insert the needle into the jugular vein. Further, it would be desirable to provide a visual indication on a display screen or other human perceptible indication of what vessel (if any) the needle has pierced. A desirable indication might include showing graphic images of the jugular and the carotid artery on the display screen so that when a person has successfully inserted the needle into the jugular vein, the screen can show a green light to indicate success, or a red light if the needle has improperly pierced the carotid artery.
Earlier attempts to implement the use of a conductive fluid in a simulated vessel to detect contact between a needle or other medical instrument with the conductive fluid identified problems related to repeated use of such a medical trainer. It was found that a phantom circuit can occur after successive uses of this type of medical trainer. Specifically, after a needle is removed from a vessel in the trainer following a previous insertion, traces of the conductive fluid can exist in the channel that remains when the needle was previously withdrawn. Also, the conductive fluid in the simulated vessels can be at a positive pressure, so that the conductive fluid leaks from the simulated vessel through the channel created by the previous needle puncture. This leaking conductive fluid can remain on the surface of the medical trainer (i.e., on its simulated epidermis or other portions of the medical trainer that are not within the simulated vessels). During a subsequent training procedure, insertion of the needle through the simulated skin of the medical trainer may enable the needle to come into contact with any residual conductive fluid on the skin or other surfaces, or the needle may cross a previous path of insertion where there is residual conductive fluid. As a result, the circuit that is used to detect the vessel into which the needle has been inserted would detect a phantom circuit that is not the result of insertion of the medical device into one of the vessels, because of the contact of the needle with this residual conductive fluid on the surface or the residual fluid remaining in the previous insertion channel. Accordingly, it would be desirable to prevent such phantom circuit detections caused by contact of a needle or other medical instrument with conductive fluid that is not within the simulated vessels of the medical trainer.
It would also be desirable to employ a conductive fluid in a vessel to determine a position of a medical device in the vessel. For example, it would be desirable to determine where in a vessel filled with a conductive fluid that a needle pierced the vessel, or to determine where a medical instrument with a conductive tip had been advanced within a vessel filled with a conductive fluid.